On Wed, 2010-12-01 at 12:21 +0800, Minchan Kim wrote: > On Wed, Dec 1, 2010 at 12:08 PM, Shaohua Li <shaohua.li@xxxxxxxxx> wrote: > > T0: Task1 wakeup_kswapd(order=3) > > T1: kswapd enters balance_pgdat > > T2: Task2 wakeup_kswapd(order=2), because pages reclaimed by kswapd are used > > quickly > > T3: kswapd exits balance_pgdat. kswapd will do check. Now new order=2, > > pgdat->kswapd_max_order will become 0, but order=3, if sleeping_prematurely, > > then order will become pgdat->kswapd_max_order(0), while at this time the > > order should 2 > > This isn't a big deal, but we do have a small window the order is wrong. > > > > Signed-off-by: Shaohua Li <shaohua.li@xxxxxxxxx> > Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxx> > > But you need the description more easily. > > I try it. Thanks, changed the description. T0: Task 1 wakes up kswapd with order-3 T1: So, kswapd starts to reclaim pages using balance_pgdat T2: Task 2 wakes up kswapd with order-2 because pages reclaimed by T1 are consumed quickly. T3: kswapd exits balance_pgdat and will do following: T4-1: In beginning of kswapd's loop, pgdat->kswapd_max_order will be reset with zero. T4-2: order will be set to pgdat->kswapd_max_order(0), since it enters the false branch of 'if (order (3) < new_order (2))' T4-3: If previous balance_pgdat can't meet requirement of order-2 free pages by high watermark, it will start reclaiming again. So balance_pgdat will use order-0 to do reclaim, while at this time it really should use order-2 This isn't a big deal, but we do have a small window the order is wrong. Signed-off-by: Shaohua Li <shaohua.li@xxxxxxxxx> Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx> diff --git a/mm/vmscan.c b/mm/vmscan.c index d31d7ce..c630349 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2450,7 +2450,8 @@ static int kswapd(void *p) } } - order = pgdat->kswapd_max_order; + order = max_t(unsigned long, new_order, + pgdat->kswapd_max_order); } finish_wait(&pgdat->kswapd_wait, &wait); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>